Articles

The migration of the water-soluble fraction of petroleum hydrocarbons in typical soils of Bashkortostan is studied. In a lysimetric model experiment, the possibility of water migration of petroleum hydrocarbons in Fluvic Phaeozems, Haplic Phaeozems and Amphiskeletic Pantocalcic Chernozems was revealed. Among the dissolved organic substances that pass into lysimetric waters from oil-contaminated soils, the components that are not extracted by hexane, but have fluorescence in water at the wavelengths typical for petroleum products are revealed. These substances differ from soluble organic matter of background soils by higher HIX humification indices and presumably represent oxidized products of transformation of petroleum hydrocarbons. Lysimetric waters from all oil-contaminated soils are characterized by biotoxicity, regardless of the presence of non-polar petroleum hydrocarbons. The toxicity T-index positively correlates with the content of dissolved organic carbon and chloride ions that accompany soils oil pollution.

Surface waterlogged soils, drained by ceramic and plastic drainage, are an analogue of large-area lysimetric installations, the drainage runoff in which is represented by gravitational waters like lysimetric waters. The drainage runoff module in the spring and autumn periods at landfills drained with plastic and ceramic drainage, and its dependence on the humidity of the year have been established. It is shown that drainage transforms the type of water regime from stagnant-washing to washing. The long-term and spatial dynamics of the removal of the silty fraction of soils and iron compounds has been studied. The removal of chemical elements with drainage runoff and its influence on the intensity of the loessivage process in agro-gray drained soils have been established.

The main components of the CO2 balance - emission from the surface, removal with lysimetric runoff, and dynamics of reserves in a 1.5 m soil layer, taking into account interphase equilibria, were quantitatively assessed in a 2-year soil-lysimetric experiment. A significant (up to 20-90%) contribution of lysimetric runoff to the total gas exchange in cold weather (autumn-winter) against the background of a small (0.3-3.7%) share during the growing season (spring-summer) is shown. Due to the unsteadiness and inertia of gas accumulation / unloading processes inside the soil, emission from the surface does not adequately reflect the gross CO2 production by the soil volume, underestimating in the spring-summer period and overestimating in autumn. The obtained 2-year correlation between emission and gross-production indicates the possibility of a 1.3-1.4-fold underestimation of the dissimilation component of the carbon cycle in the traditional emission assessment of soil respiration.

The theoretical equation of the concentration of trace element compounds entering the soil with atmospheric precipitation as a function of depth and time is tested on the example of data on the long-term dynamics (1965, 1995, 2006, and 2013) of Cu, Ni and Mn compounds in the soil profile under artificial phytocenoses of the MSU soil lysimeters. The obtained results indicate the possibility of using an analytical model for predicting the content of heavy metals in the soil profile.

Mineralization rates of soil organic matter (SOM) decomposition of non-remediated and remediated oil)polluted, as well as background soils from the main types of West Siberian middle taiga’s ecosystems were measured in laboratory experiments. Rates of SOM mineralization were measured by alkali absorption of CO₂ released from wet soil samples at 20°C (basal respiration). Because of linear character of cumulative curves of CO₂ release SOM mi neralization rates were expressed by mineralization index K1 equal to the annual amount of CO₂ released per 1 gramm of soil. K1 values varied in a range 0,123—1,578 mg СО₂/g/day. Highest value was found in background forest soil, lowest — in oil-polluted peat soil with extremely high oil content (544 g/kg). K1 values negatively correlated (K = –0,57) with oil content. SOM mineralization rates in remediated oil)polluted peat soils varied in a range — 0,31—0,85 mg СО₂/g/day

Abundance and diversity of soil saprotrophic bacteria complexes were monitored for two years on the territory of one of the large industrial cities of the European North of Russia, Syktyvkar. The work was carried out before and after quarantine in connection with the COVID-19 pandemic. The capital of Komi is characterized by a high population, and by tense environmental conditions according to the ecological standard. Studies were conducted in 2019—2020. Topsoils (0—10 cm) of urbanozems, horizon A in the park area in the urban space, as well as zonal undisturbed podzolic soil were analyzed. Comparison of the two)year monitoring results demonstrated a marked increase in the number and diversity of saprotro) phic bacteria complexes in 2020 both in urban and control soils (topsoil, 0—10 cm).

Detailed studies of Enterobacteriaceae demonstrated a decrease in the share of opportunistic (Enterobacter agglomerans, Citrobacter europaeus, Klebsiella oxytoca, Serratia marcescens, etc.) as well as fecal coliforms (Escherichia coli, Enterococcus faecalis) in urbanozems in 2020 — a consequence of a sharp and prolonged decrease in the anthropogenic impact on the environment. It can be viewed as a manifestation of the soil ability to “self-purification” when anthropogenic impact on the environment reduces.